New Softer Shocks

[JamesW]

Don't know if this is the correct forum but here goes anyway.  I would like to replace the OEM shocks on my early R1100RSL with softer more compliant units.  I'm more interested in a softer ride at this stage of the game than I am about blitzing the twisties. 

 

Thanks, James

[dirtrider]

50 minutes ago, JamesW said:

Don't know if this is the correct forum but here goes anyway.  I would like to replace the OEM shocks on my early R1100RSL with softer more compliant units.  I'm more interested in a softer ride at this stage of the game than I am about blitzing the twisties. 

 

Thanks, James

Afternoon James

 

I can't believe that your original shocks have much compression damping left (they didn't have a lot to begin with) so you will probably more need to work with your springs than shocks.

 

What tire pressures are you running as that probably has more input on a harsh ride than anything.

 

Do what you can with tire pressures then if still too harsh  maybe call one of the aftermarket suspension companies to see what they suggest for a spring/shock package.

 

Also, if you store that motorcycle on the center stand for long periods (especially throughout big temperature change seasons)  then you might bleed the trapped air out of your front forks with the motorcycle sitting on the suspension.   It doesn't take much trapped air pressure in the forks to add front suspension stiffness due to the added pressure in the forks.   (basically you have air forks + the shock spring) 

[JamesW]

Well, I run 39 in front and 41 in the rear.  Great for tire life.  When I said shocks I meant spring/shock package or strut.  Don't really trust talking to sales folks about after market products so was hoping someone here had some first hand experience with after market suspension products.

 

I don't ride much in winter since it gets kind of wet in these parts so yeah the bike sits in the shop which is at a constant 65 degrees all winter long so not exposed to temp changes.

 

With telelever suspension the front forks only provide front wheel steering input not suspension and are a non-maintenance item so I can't see trapped air as an issue.  I might just to say I did change the fork oil one of these days.

[szurszewski]

You could call Ted Porter. While he does sell shocks I don’t think I’ve ever heard/read about anyone considering him a salesperson. He’s a motorcycle person who happens to have a well respected business. I’ve only spoken with him a few times but each experience was excellent and he is very clear in laying out options and explaining what each of those options will and won’t do. Everything I’ve purchased from him has done exactly what he said it would. 

[dirtrider]

10 hours ago, JamesW said:

Well, I run 39 in front and 41 in the rear.  Great for tire life.  When I said shocks I meant spring/shock package or strut.  Don't really trust talking to sales folks about after market products so was hoping someone here had some first hand experience with after market suspension products.

 

I don't ride much in winter since it gets kind of wet in these parts so yeah the bike sits in the shop which is at a constant 65 degrees all winter long so not exposed to temp changes.

 

With telelever suspension the front forks only provide front wheel steering input not suspension and are a non-maintenance item so I can't see trapped air as an issue.  I might just to say I did change the fork oil one of these days.

Morning  James

 

That 39 in front and 41 in the rear is probably most of your harsh ride problem, That is WAY more pressure than I used to run in my old 1100 R bikes. You might try 32 front & 36 rear as a test. 

 

As for the front fork air pressure not being a problem. Way back I used to run some of my dirt bikes with no front springs at all  (just air pressure in the front forks) basically air forks. 

 

Air (above normal atmospheric pressure) in the front fork tube IS a spring, the higher the air pressure in the tubes the higher the spring load added. (this is basically how hydraulic cylinders work only they use non-compressible fluid instead of compressible air)

 

If you have trapped air pressure in the front forks that is just like putting additional springs inside the front fork tubes.

 

It won't be a lot but could be enough to increase front ride harshness, you want "0" air  pressure (compared to atmospheric) in the forks at nominal ride height (service manual tells you how to bleed the air out). Why would the service manual even mention it if it wasn't important to bleed the excess air out?

 

 If you store the motorcycle on the center stand you basically have the forks extended, so even without a large temperature change they can take in some air over time to allow the forks to be at atmospheric  pressure extended (the seals are basically designed to keep the oil in not keep long term air out). So when you drop it onto the wheels that  nominal atmospheric  pressure in the (extended fork) becomes pressurized. Not a real big deal but does add spring load to the forks, now add to that the fact that the air was taken in at a 30° or 40° lower temperature (you get about 1 psi increase in pressure for every 10° temperature increase so you now have an additional 3 or 4 PSI pressure increase on top of the extended fork air take-in pressure increase. Your inner fork tube diameter (converted to area) is the piston size so that can add up. Not significant but enough to make the ride harsher. 

 

On my hard usage dirt bikes I actually have air bleeders on the front forks to let air pressure build-up out as they keep increasing in pressure as the internal air heats up when riding hard off-road.

 

 

 

  

[Lowndes]

6 hours ago, szurszewski said:

You could call Ted Porter. While he does sell shocks I don’t think I’ve ever heard/read about anyone considering him a salesperson. He’s a motorcycle person who happens to have a well respected business. I’ve only spoken with him a few times but each experience was excellent and he is very clear in laying out options and explaining what each of those options will and won’t do. Everything I’ve purchased from him has done exactly what he said it would. 

 

JamesW,

 

My experience with Ted Porter is exactly the same as Suzurzewski's.  I've purchased two sets of replacement "shocks" (with springs) for two of my '99 era BMW's and couldn't be happier with both.  I called him about the first set ('99 R1100S) but had to leave a message.  He called me back at about 10 PM on a Saturday night and we talked about 45 minutes, him asking questions about my weight, gear, any other changes to the bike, riding style, roads traveled, road surfaces, and my tires.  He discussed the pro' and cons of several different brands of units that he sold but recommended Wilbur units which were not the most expensive.  Yes, he runs a business and sells shocks, but he is most interested in getting you happy with the outcome, even if it's just an air pressure adjustment like what Dirtrider suggests. 

 

I'm in "sales" and can tell you that credibility and trust with my "customers" is PARAMOUNT,  because I want to be doing business with them for a long time.  My job is to help them find the best solution for their customer even if it is a competitor's product.  I'll frequently give them the name and contact info of the competition if I have personal experience with or knowledge of the item.  You don't have to buy from anyone but you might call and at least listen to what Ted Porter can tell you about your suspension.  He will discuss motorcycle suspension as long as you care to.  And it's a free call.

 

I had to replace the fork seals on my '00 K12RS last week (TeleLever front forks, also - no springs inside) and noticed air pressure (like what Dirtrider referred to above) inside when I opened the top cap.  No idea how it got in there.  Too much pressure for baro or temp differences.  Also,  I did recently add an "air system" to the front forks on my '06 Honda ST1300 to correct a set of way-too-soft front springs that made for a mushy front end and did not inspire confident handling.  Works great.  Air is a perfect spring, infinately progressive and adjustable.

 

Your front "shock" may have a preload adjustment for the spring.  My Clymer doesn't say one way or the other for the OEM on your model so I guess it doesn't unless it has been replaced by a PO.  You should be able to see the base of the unit where the adjustment would be with a flashlight.

 

 

[dirtrider]

39 minutes ago, Lowndes said:

Your front "shock" may have a preload adjustment for the spring.  My Clymer doesn't say one way or the other for the OEM on your model so I guess it doesn't unless it has been replaced by a PO.  You should be able to see the base of the unit where the adjustment would be with a flashlight.

 

Afternoon Lowndes

 

A preload adjustment really doesn't do much for spring load or rate (unless the up travel is maxed out or lowered enough so it contacts the jounce bumper early)  the motorcycle just increases in height or lowers in height in relation to the preload adjuster setting but the vehicle weight still loads the spring to the same loaded spring height.  

 

Or put another way-- as long as the spring is free to travel up or down without contacting it's up or down limits then preload adjustment won't effect the spring's loaded height, load, or rate.

 

Adding preload can raise the motorcycle on the spring (but still the same spring loaded length), or allow farther down travel if no extra vehicle  weight is added, or can allow the motorcycle to go back to the same ride height if more weight is added to that end of the motorcycle (the added weight does change the springs loaded height).     

[JamesW]

Morning to you D.R.,

You are so right about my bike and air bleed of front forks.  I found the info in the factory service manual specific to the RS model.  The front forks should be air bled while on the center stand.  So, I unscrewed the black plastic caps on top of the fork tubes and with a 10mm socket withdrew the air bleed screws which have "O" ring seals and PSSSST.... out came trapped air and with quite a bit of built up pressure.  Thanks so much for pointing this out to me.  On the topic of tire pressure I agree that running the pressures I do makes for a harder ride but I do get much less front tire cupping and improved tire life. I guess everything is a trade off.  As far as the age of my shocks being an issue my bike only has 12.5K original miles all put on by me since I purchased the bike from the original owner in 2012.  Hard to believe but the bike had not been even started not once since it left Berlin in August of 1993 until I became the owner in 2012.  You should have seen what remained of the gas used to dyno check the bike at the factory final acceptance inspection. Not pretty!

 

The front shock has no pre load or any adjustability on the RS model according to the service manual and close inspection has confirmed this.  

 

Lowndes, thanks for the reference and good recommendation on who to contact for good info on after market shocks.  I'll contact Ted Porter next week for sure.

 

Man, am I going to pay close attention to those air bleed screws from now on.  Thanks again D.R. I really appreciate your wisdom and experience and I've learned much over the years from reading your posts.  On my RS with the telelever I've payed little attention to anything related to the front forks I mean they don't even have springs and as I understand it or should I use past tense here: understood it, the forks aren't considered a service item on the RS of this vintage.

[King Herald]

I've been toying with the idea of new shocks for my 80,000 miles 97' 1100r, because they are basically worthless for damping etc, and the ride is so harsh. The cost is nigh on what the old girl is worth though, so I'm wondering whether to add the cost and go for something with far less miles, and a later model, maybe a GS.

However, I will have a look into this air bleed screw. I've had the forks apart a few times and never noticed that feature. They are pitted from corrosion's, and do leak a little oil on long hot rides, but I'd wager the oil itself is enough to seal the air from getting out.  And I may let a bit more air out of the tyres too. I only ever ride one up, sometimes with baggage for touring. 

[dirtrider]

2 hours ago, JamesW said:

 On my RS with the telelever I've payed little attention to anything related to the front forks I mean they don't even have springs and as I understand it or should I use past tense here: understood it, the forks aren't considered a service item on the RS of this vintage.

Afternoon James 

 

While there is no given service interval on the BMW  1100RS, that doesn't mean that you should service the front fork oil  every so many years. 

 

The fork oil is not used for damping control but is used to lubricate the internal slider bushings. Once the fork oil gets older & picks up little particles from the bushing wear & just general age breakdown it then allows faster bushing wear. 

 

On your RS those fork bleeders might be large enough to get small diameter plastic hose down in there & suck the old oil out. If not then the next time you have the front wheel off (axle removed)  then there  s-h-o-u-l-d be some fork drain screws up  through an access hole in top the axle hole. If your early RS has those drain screws don't fight them too much as I have seen the fork threads strip out. So if they don't loosen easily then get the old oil out another way.   

[JamesW]

I don't want to belabor the point and for certain there was what seemed to be quite a bit of pressure built up in the forks but I can't understand the physics involved. How could air enter the fork tubes and not be able to escape.  I mean what goes in must come out right?  Also, when the forks heat up pressure will increase but also would it not decrease when the temperature drops?  Not to be a smarty but back in the dark ages I did take the required one year of college physics that being heat light and sound as well as mechanics like levers and fulcrums and such.  It might be kind off interesting to replace the vent screws with air fittings and install a pressure gauge with a pressure release tab like on a compression gauge and monitor this phenomena awhile. On the other hand maybe the best thing is just to view this as another one of life's mysteries and just let it go. 

 

Wellll, just one more question:  Why doesn't this pressure phenomena show itself on other motorcycles like for example the one parked next to my RS that being the, admitted somewhat inferior to the pride of the fatherland, beast called an FJR?

[dirtrider]

57 minutes ago, JamesW said:

I don't want to belabor the point and for certain there was what seemed to be quite a bit of pressure built up in the forks but I can't understand the physics involved. How could air enter the fork tubes and not be able to escape.  I mean what goes in must come out right?  Also, when the forks heat up pressure will increase but also would it not decrease when the temperature drops?  Not to be a smarty but back in the dark ages I did take the required one year of college physics that being heat light and sound as well as mechanics like levers and fulcrums and such.  It might be kind off interesting to replace the vent screws with air fittings and install a pressure gauge with a pressure release tab like on a compression gauge and monitor this phenomena awhile. On the other hand maybe the best thing is just to view this as another one of life's mysteries and just let it go. 

 

Wellll, just one more question:  Why doesn't this pressure phenomena show itself on other motorcycles like for example the one parked next to my RS that being the, admitted somewhat inferior to the pride of the fatherland, beast called an FJR?

Evening James

 

The main reason that air can get in & not out is the design of the fork seals.  The fork seal lips are mainly designed to keep the oil in so they are shaped that way. 

 

As long as there is positive pressure inside the fork tubes then that forces the seals tighter to the fork tubes so they seal very tightly (won't allow any air out). 

 

When you put the motorcycle on the center stand the volume area inside the fork tubes expands so that lowers the internal air pressure. If it goes lower than the atmospheric pressure outside the forks then the seals release slightly & allow the air pressure to slowly equalize.

 

Then next time you put it on the wheels you have positive pressure inside the forks. This stays about the same until you put it back on the center stand for an extended time period & the ambient air temperature drops. This allows the fork internal pressure to drop even lower as the trapped air inside the forks  contracts so again the outside atmospheric pressure is higher so it again equalizes, then you have higher pressure yet inside the forks the next time the weather gets warm & you put it on it's wheels.

 

As far as pressure release tabs?-- That is what I run on my dirt bikes, they are just simple push button pressure release  valves. After a spirited  off-road ride I just wait a few minutes (usually after short break to allow my hanging out tongue to retract back into my mouth) this allows the the fork oil  to drain back away from the release valves, I then push the buttons to release the built up internal pressure. The hotter the forks get the more pressure that I have to let out.  

 

I have tried just venting the fork tops through fuel filters directly to atmosphere but I usually end up with some internal fork oil venting with the air so the pressure release push buttons seem to work best.    

 

It will effect all motorcycles but the BMW's  with no fork springs seem to be the worst.

 

  

 

 

[JamesW]

Afternoon D.R.,

Thanks for taking time to explain this phenomena to me, most interesting, and I'm going to look into pressure release tabs although I do like the finished appearance with the black plastic covers.  

 

Really good detailed explanation, thank you, and I'm going to pay attention to this pressure build up. It never would have occurred to me to ever consider this.

[King Herald]

I just had a go at releasing my pressure. I cut a 3mm hex wrench down so it will fit into the tiny gap to the release screw. Very fiddly to do, without first releasing the fork leg from the top.  One screw came out with a little pop, but the other made no noise. 

The hole is too small to adapt a simple pressure release to I think, 4mm. Maybe a small grease nipple could be fit, and release pressure by pushing the ball in with a pointy thing. 

 

[JamesW]

Herald,  maybe your seals are so bad that the don't seal good enough to trap air anyway in which case maybe you're good to go and no need for bleeder screws.I like my bleeder screws for their location a lot better than yours for sure.  

[King Herald]

On 6/8/2021 at 8:58 PM, JamesW said:

Herald,  maybe your seals are so bad that the don't seal good enough to trap air anyway in which case maybe you're good to go and no need for bleeder screws.I like my bleeder screws for their location a lot better than yours for sure.  

 

The seals are great.....but the fork legs have more pits than the surface of the moon.